System for electrically stimulating target neuronal cells of a living animal in vivo

ABSTRACT

In one example, a system electrically stimulates target cells of a living animal using an elongated structure, a modulation circuit and a light pathway such as provided by an optical fiber arrangement. The elongated structure is for insertion into a narrow passageway in the animal such that an end of the elongated structure is sufficiently near the target cells to deliver stimulation thereto. The modulation circuit is for modulating the target cells while the elongated structure is in the narrow passageway, where the modulation circuit is adapted to deliver viral vectors through the elongated structure for expressing light responsive proteins in the target cells. The light pathway is used for stimulating the target cells by delivering light to the light-responsive proteins in the target cells.

RELATED PATENT DOCUMENTS

This application is a divisional of U.S. patent application Ser. No. 12/185,624, filed Aug. 4, 2008, which claims the benefit, under 35 U.S.C. § 119(e), of U.S. Provisional Patent Application Ser. No. 60/953,920, entitled Optical Tissue Interface Method and Apparatus for Stimulating Cells and filed on Aug. 3, 2007; The contents of U.S. patent application Ser. No. 12/185,624 and U.S. Provisional Patent Application Ser. No. 60/953,920, including the Appendix therein, are fully incorporated herein by reference.

U.S. patent application Ser. No. 12/185,624 also claims priority, as a CIP under 35 U.S.C. § 120, to the following patent documents which are also individually incorporated by reference: U.S. patent application Ser. No. 11/651,422, filed on Jan. 9, 2007 and entitled, System for Optical Stimulation of Target Cells), which is a CIP of U.S. patent application Ser. No. 11/459,636, filed on Jul. 24, 2006 and entitled, Light-Activated Cation Channel and Uses Thereof, which claims the benefit of U.S. Provisional Application No. 60/701,799, filed Jul. 22, 2005; and U.S. patent application Ser. No. 12/041,628, filed on Mar. 3, 2008 and entitled, Systems, Methods And Compositions For Optical Stimulation Of Target Cells, which claims the benefit of U.S. Provisional Application No. 60/904,303, filed on Mar. 1, 2007.

GOVERNMENT RIGHTS

This invention was made with Government support under contract OD000616 awarded by the National Institutes of Health. The Government has certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates generally to systems and/or methods for stimulating target cells optically and more particularly to an optical neural interface, system and method for delivery of genetic modifiers and optical stimulus to target cells.

BACKGROUND AND OVERVIEW

The stimulation of various cells of the body has been used to produce a number of beneficial effects. One method of stimulation involves the use of electrodes to introduce an externally generated signal into cells. For example, in connection with electrode-based brain stimulation techniques, the distributed nature of neurons may be responsible for a given mental process. Also, different types of neurons reside close to one another such that only certain cells in a given region of the brain may be activated while performing a specific task. Not only do heterogeneous nerve tracts move in parallel through tight spatial confines, but the cell bodies themselves may exist in mixed, sparsely embedded configurations. This distributed manner of processing is an issue in attempts to understand canonical order within the Central Nervous System (CNS), and can make neuromodulation a difficult therapeutic endeavor. Due to this architecture of the brain, there are issues concerning use of electrode-based stimulation which is relatively indiscriminate with regards to the underlying physiology of the neurons that they stimulate. Instead, physical proximity of the electrode poles to the neuron is often the single largest determining factor as to which neurons will be stimulated.

Electrode placement and mechanical stability can also be an important influence on the effectiveness of electrode stimulation since location often dictates which neurons will be stimulated, and flawed location/stability can result in lead migration of the electrodes from the targeted area. Moreover, after a period of time within the body, electrode leads frequently become encapsulated with glial cells, raising the effective electrical resistance of the electrodes, and hence the electrical power delivery required to reach targeted cells. Compensatory increases in voltage, frequency or pulse width, however, may spread electrical current and result in increases in unintended stimulation of additional cells.

In connection with work by the named inventor(s) of this patent document, recently discovered techniques allow for stimulation of cells resulting in the rapid depolarization of cells (e.g., in the millisecond range). One method of stimulus uses photosensitive bio-molecular structures to stimulate target cells in response to light. For instance, light activated proteins can be used to control the flow of ions through cell membranes. Ion channels and ion pumps are cell-membrane proteins that control the transport of positively or negatively charged ions (e.g., sodium, potassium and chloride) across the cell membrane. Ion channels play an important part of various animal and human functions including signaling and metabolism. Using optically responsive ion channels or pumps to facilitate or inhibit the flow of positive or negative ions through cell membranes, the cell can be briefly depolarized, depolarized and maintained in that state, or hyperpolarized. Neurons are an example of a type of cell that uses the electrical currents created by depolarization to generate communication signals (i.e., nerve impulses). Other electrically excitable cells include skeletal muscle, cardiac muscle, and endocrine cells.

Various techniques can be used to control the depolarization of cells such as neurons. Neurons use rapid depolarization to transmit signals throughout the body and for various purposes, such as motor control (e.g., muscle contractions), sensory responses (e.g., touch, hearing, and other senses) and computational functions (e.g., brain functions). Thus, the control of the depolarization of cells can be beneficial for a number of different purposes, including (but not limited to) psychological therapy, muscle control and sensory functions. For further details on specific implementations of photosensitive bio-molecular structures and methods, reference can be made to “Millisecond-Timescale, Genetically Optical Control of Neural Activity”, Nature Neuroscience 8, 1263-1268 (2005). This reference discusses use of blue-light-activated ion channel channelrhodopsin-2 (ChR2) to cause calcium (Ca++)-mediated neural depolarization, and is fully incorporated herein by reference. Other applicable light-activated ion channels include halorhodopsin (NpHR), in which amber light affects chloride (Cl−) ion flow so as to hyperpolarize neuronal membrane, and make it resistant to firing.

SUMMARY

Various aspects of the invention address the above-discussed issues and others as would become apparent from the discussion that follows.

According to one embodiment, the present invention is directed to a system for electrically stimulating targeted excitable cells of a living animal using light to alter the electrical behavior of the cells.

According to one embodiment, a system electrically stimulates targeted excitable cells of a living animal by using an elongated structure, a modulation circuit and a light pathway such as provided by an optical fiber arrangement. The elongated structure is for insertion into a narrow passageway in the animal such that an end of the elongated structure is sufficiently near the target cells to deliver stimulation thereto. The modulation circuit is for modulating the target cells while the elongated structure is in the narrow passageway, where the modulation circuit is adapted to deliver viral vectors through the elongated structure for expressing light responsive proteins in the target cells. The light pathway is used for stimulating the target cells by delivering light to the light-responsive proteins in the target cells.

According to another embodiment, a method electrically stimulates target cells of a living animal in vivo. An elongated structure is inserted into a narrow passageway in the animal such that an end of the structure is sufficiently near the target cells to deliver stimulation thereto. While the elongated structure is in the narrow passageway, viral vectors are delivered through the elongated structure for expressing light responsive proteins in the target cells. After delivering the viral vectors, an optical fiber is inserted through the elongated structure. The target cells are stimulated by using the optical fiber to deliver light to expressed light responsive proteins in the target cells.

According to one embodiment, an elongated structure is inserted into a narrow passageway in an animal for modulating of the activity of electrically-excitable cells. Growth of light-gated ion channels or pumps is induced in the membrane of a nerve cell located at a selected target within the body. At least one flash of light is directed upon the light-activated proteins so as to modulate the function of the target or surrounding cells.

According to one embodiment, an arrangement is implemented with an elongated structure inserted into a narrow passageway in an animal for modulating of the activity of electrically-excitable cells and for actively growing light-gated ion channels or pumps in the membrane of a nerve cell located at a selected target within the body. A light source is used for directing at least one flash of light upon the light-activated proteins so as to modulate the function of the target or surrounding cells.

According to one embodiment, a system electrically stimulates target cells of a living animal in vivo. The system includes an elongated structure for insertion into a narrow passageway in the animal such that an end of the elongated structure is sufficiently near the target cells to deliver stimulation thereto. A modulation circuit is included for modulating the target cells while the elongated structure is in the narrow passageway, the modulation circuit including means for delivering viral vectors through the elongated structure for expressing light responsive proteins in the target cells. An optical fiber arrangement is included for stimulating the target cells by delivering light to the light-responsive proteins in the target cells.

According to one embodiment, a system electrically stimulates target neurons in a brain in vivo via the skull. The system has an elongated structure having two ends and a passage extending between the ends. The elongated structure is sufficiently small for insertion through the skull and into the brain. A mount secures the elongated structure to the skull. A reservoir holds viral vectors for expressing at least one of ChR2 and NpHR in the target cells. A delivery device moves the viral vectors from the reservoir through the passage and to the target neurons. An optical fiber light-delivery arrangement includes an optical fiber for insertion through the passage and a light generator for sourcing light through the optical fiber to stimulate the target cells and to activate the at least one of ChR2 and NpHR expressed in the target cells. The light delivered through the optical fiber illuminates an area of the brain in which the target neurons are located.

The above summary is not intended to describe each illustrated embodiment or every implementation of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of the detailed description of various embodiments of the invention that follows in connection with the accompanying drawings, in which:

FIGS. 1A and 1B are diagrams of respective arrangements for application to mammalian skulls, each arrangement including an optical neural interface according to an example embodiment of the present invention;

FIG. 2 is a flow chart showing one example of a method for optically targeting cells in a selected patient, according to the present invention;

FIG. 3A shows a diagram of test setup involving mouse whisker deflection, consistent with an example embodiment of the present invention;

FIG. 3B shows detected whisker deflection relative to the stimulating light, consistent with an example embodiment of the present invention;

FIG. 3C shows detected whisker deflection with and without CHR2 and with and without stimulating light, consistent with an example embodiment of the present invention;

FIG. 4A shows electrode-based cell stimulation; consistent with an example embodiment of the present invention;

FIG. 4B illustrates optical stimulation of genetically-targeted cells, consistent with an example embodiment of the present invention;

FIG. 5 shows an example of an optical neural interface used for neural stimulation of the brain, according to an example embodiment of the present invention;

FIG. 6 shows an example of an optical neural interface used for endocardial stimulation of the heart; according to an example embodiment of the present invention;

FIG. 7 shows an example of an optical neural interface used for epicardial stimulation of the heart; according to an example embodiment of the present invention;

FIGS. 8a through 8e illustrate cell recordings that were obtained from a ChR2+ layer 5 motor neuron in acute brain slices that were prepared and processed according to the present invention;

FIGS. 9A and 9B are graphs showing the effective light transmission/intensity for tissue penetration, as may be useful in connection with estimating expected tissue volume that is activated optical neural interfaces implemented and used in accordance with the present invention; and

FIGS. 10A, 10B, 10C and 10D are diagrams showing the effectiveness of evoking whisker deflections as it relates to, optical neural interface implanted and tested in mice according to the present invention.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION

The present invention is directed to practical application of a variety of optically-based stimulus systems, and the invention has been found to be particularly suited for use in systems and methods dealing with stimulation of target cells using a cannula (a tube for insertion into a body cavity or into a duct or vessel) to deliver optically responsive genetic modifiers and optical stimulus to target cells. While the present invention is not necessarily limited to such applications, various aspects of the invention may be appreciated through a discussion of various examples using this context.

Recently discovered techniques allow for stimulation of cells resulting in the rapid depolarization of cells (e.g., in the millisecond range). Such techniques can be used to control the depolarization of cells such as neurons. Neurons use rapid depolarization to transmit signals throughout the body and for various purposes, such as motor control (e.g., muscle contractions), sensory responses (e.g., touch, hearing, and other senses) and computational functions (e.g., brain functions). Thus, the control of the depolarization of cells can be beneficial for a number of different biological applications, among others including psychological therapy, muscle control and sensory functions. For further details on specific implementations of photosensitive bio-molecular structures and methods, reference can be made to the above-referenced patent documents by Karl Deisseroth et al., which are fully incorporated herein by reference. These references discuss use of blue-light-activated ion-channel channelrhodopsin-2 (ChR2) to cause calcium (Ca++)-mediated neural depolarization. Other applicable light-activated ion channels include, for example, halorhodopsin (NpHR) in which amber light affects chloride (Cl−) ion flow so as to hyperpolarize aneuronal membrane, and make it resistant to firing.

Certain aspects of the present invention are directed to stimulating target cells via optogenetic excitation and/or to optogenetic stabilization. Optogenetic excitation refers to a combined optical and genetic approach that increases the depolarization rate of the targeted cell population. While not necessarily limited to this application (or agent), one approach to achieving such increases involves expression of ChR2 in targeted cells, and blue light, emitted for example, from a surgically implanted hardware device, is flashed to trigger depolarization. Optogenetic stabilization refers to a combined optical and genetic approach that decreases the depolarization rate of the targeted cell population. One approach to achieving such decreases is to cause NpHR to be expressed in targeted cells. Yellow light emitted for example, from a surgically implanted hardware device, is provided to hyperpolarize the membrane and prevent depolarization. Optogenetic stabilization is not necessarily limited to any particular genetic agent and may apply to other appropriate optogenetic agents as well as to variations on the delivery of light thereto.

Consistent with one example embodiment of the present invention, a system is implemented for providing in vivo stimulus (e.g., via optogenetic excitation and/or to optogenetic stabilization) to target cells. The system provides an elegant solution for both modifying the target cells to be optically responsive and stimulating the target cells optically. One end of a cannula may be stereotactically or otherwise guided near the target cells. Viral vectors or other cell modifiers are inserted through the other end of the cannula to modify the target cells to be optically responsive. The cannula is then used to guide an optical delivery device, such as fiber optics, to the same site that the viral vectors were delivered. Optical stimulus is provided to the target cells using the optical delivery device. Generally, these and other applications are discussed herein in the context of live animals; however, other applications (e.g., postmortem or otherwise) are also envisioned.

For the delivery of light to photo-sensitive neurons and other cell types, there are several different possible light sources, each having its own benefits with respect to power, wavelength, heat production, optical coupling, size, and cost. A few example light sources include, but are not limited to, lasers (gas, crystal, and solid-state) and light-emitting diodes (LEDs). Optical fibers have many properties that make them beneficial for the delivery of light deep within tissue such as the brain. They are thin, light-weight, flexible, and transmit light with negligible loss over short distances. In addition to single optical fibers, fiber bundles or arrays of optical fibers can be useful for light delivery depending on the size and location of the tissue targeted. For some applications direct light delivery an LED may be preferred. For example, treatment of cortical brain tissue or heart tissue LED illumination may be efficacious.

In one embodiment, a system that includes a power supply, control circuit, light source, and light conduit, could be implanted. This can be useful for minimizing infection and improving patient convenience. In order to facilitate such implantation, the light source/housing/power supply “box” can be designed on the order of the largest current neurostimulators. The supply box can also be designed to either be rechargeable or to have a long battery life (e.g., 3 years or more).

According to one embodiment of the presenting invention, an implantable cylindrical structure (e.g., a cannula or a cathether) includes multiple parallel fibers terminating around the circumference of a cylindrical structure, over a span of several millimeters. This allows for “steering” of light to various portions and allows intensity control by activation of more or fewer fibers. Such multiplexing of light through multiple fibers can also be useful for spatial control of light delivery.

One such device can be reinforced for protection of the light guides so as to survive clumsy handling by surgeons and the bending/buckling stresses encountered inside a mobile animal/human body. In one instance, the device can be arranged with optical connectors that allow replacement of the light guide.

One such device may also be arranged to facilitate the integration of electrical recording with optical stimulation. In a particular instance this is accomplished using different populations of fibers, and an electrical recording component which could either be an array of microelectrodes (a la Cyberkinetics/Utah) or larger macroelectrodes to record local field potentials.

According to another embodiment, microfluidic integration can be useful, given the potential need for “booster” injections of vector. This can be particularly useful for delivery mechanisms that require periodic delivery, such as adenovirus-based delivery.

According to one embodiment of the present invention, the cannula may be fixed to a skull (mammalian or otherwise) using adhesive, or other suitable attachment mechanisms, prior to the delivery of the (ChR2/NpHR) solution. This can be useful for maintaining the location for the end of the cannula located near the target cells during the entire procedure. The solution may be administered directly through the cannula or through a separate deliver lumen or tube that may be inserted through the cannula. The first lumen may be subsequently removed and fiber optics or a lens and mirror arrangement may be inserted into the lumen.

As applied to human skull and a rat skull, FIGS. 1A and 1B provide an overview of an optical neural interface, in accordance with the present invention. FIGS. 1A and 1B illustrate similar optical neural interfaces which are mounted on a mammalian skull, showing an optical fiber guide, optical fiber inserted in the guide, and blue light transmitted to the cortex. As discussed in more detail below, optical neural interfaces, have a wide variety of applications for studies and treatment of a wide variety of functions and disorders. These functions and disorders are typically associated with specific neurons or anatomic locations.

FIG. 1A illustrates examples of several example anatomic locations for interventions in accordance with the methods herein described. An MRI image or patient 100 is shown in cross-sectional plane 110. Brain 140 contains numerous regions to which the methods detailed herein describe. As representative examples, five such anatomical regions and associated applications are illustrated. Brain region 115 depicts Brodmann Area 25, a depression treatment target as described below. Brain region 120 is the genu of the anterior cingulate, and a target for drug addiction treatment as described below. Brain region 125 is the prefrontal cortex, and a target for conditions including depression, as described below. Brain region 130 is anterior cingulate and corresponds with Brodmann Area 24, which is a target for pain disorders, as well as OCD and depression as described below. Brain region 135 is posterior cingulate gyms, and is one of the targets for Alzheimer's disease, as described below.

In the specific case of the rat (FIG. 1B), two weeks prior to testing, a lentivirus carrying the ChR2 gene is fused to mCherry under control of the CaMKIIα promoter as injected through the fiber guide. FIGS. 1B(i) and 1B(ii) show a schematic of the stimulated region with the optical fiber tip flush with the fiber guide and blue light illuminating the deeper layers of motor cortex. Only glutamatergic pyramidal neurons that are both in the cone of illumination and genetically ChR2+ will be activated to fire action potentials. FIG. 1B(iii) shows the rat with the optical neural interface implanted, and showing blue light transmitted to target neurons via the optical fiber. FIG. 1B(iv) is a close-up view of the optical neural interface showing fiber guide attached with translucent cranioplastic cement. Note that no scalp or bone is exposed. FIG. 1B(v) is a low-power mCherry fluorescence image of an acute brain slice showing the rat motor cortex after removal of the optical neural interface. The edge of the potential space created by the fiber guide is demarcated with a dashed line. Numerous mCherry+ neurons around the distal end of the fiber guide are present. The scale bar is 250 μm. FIG. 1B(vi) is a high-power image of mCherry+ neurons at the edge of the fiber guide potential space, showing membrane-localized fluorescence characteristic of ChR2-mCherry fusion protein expression.

As an example, FIG. 2 outlines a set of basic steps for one method that may be used in connection with the embodiments of the present invention. In step 205, the patient is selected or diagnosed as having a functional disorder of electrically-excitable cells, from a large number of possibilities, including those described herein. As part of this process, the neural circuitry, physiological feedback loops and associated mechanism of the disorder may be considered. In step 210, an applicable optogenetic approach is selected for the specific functional disorder. For example, in the case that the primary source of the problem is a hypoactive cell population, the selected approach might be an optogenetic excitation stimulation method to stimulate underactive cells, or the selected approach might be an optogenetic stabilization stimulation method to suppress another group of cells that serves to inhibit the underactive cells. In step 215 the targeted anatomy that corresponds with the known disease state and treatment strategy is identified within the actual patient. This may be done, for example, by direct visualization such as an open craniotomy or endoscope placement, or accomplished via functional imaging modalities such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), and registered to the patient via surgical image guidance systems as are known in the art (for example, the StealthStation™ by Medtronic Navigation, of Louisville, Colo.). In step 220 a gene for light-sensitive ion channels or pumps, such as ChR2 or NpHR, is surgically applied to the appropriate anatomical location. As described in the above-referenced patent documents (by Karl Deisseroth et al.), for example, for use in the brain, injections of lentiviruses can be used to selectively express the Channelrhodopsin-2 (ChR2) protein in excitatory neurons. ChR2 is a genetically expressible, light-activated cation channel which has been previously developed for use in mammals, that can give rise to nontoxic, light-driven stimulation of CNS neurons on a timescale of milliseconds, allowing precise quantitative coupling between optical excitation and neuronal activation. The genetic specificity is achieved by using a transcription promoter that is specific to excitatory neurons (CamKIIα). Using this method ChR2 is expressed in excitatory neurons and not inhibitory neurons or glial cells.

In step 225, the light-pulsing hardware is surgically inserted and, optionally implanted. An example of such light pulsing hardware can include an optical fiber coupled to a light source such as a laser diode or LED (as in FIG. 1). The target cells are then illuminated via the fiber coupled light source. An example of such an optical neural interface (ONI) is used to activate ChR2 in an intact animal brain. The interface consists of an optical fiber guide stereotactically mounted to the skull with an optical fiber inserted through the guide. The fiber guide is composed of a cannula embedded in a mounting pedestal. For viral transduction of neurons, the fiber guide serves as an injection cannula to deliver the viral vector to the motor cortex. Then following expression of ChR2, the cannula is used to guide the optical fiber to the correct location, positioning the tip so the light beam is registered with the ChR2+ neurons. By using the same cannula for viral delivery and positioning of the optical fiber, the system ensures that the light beam is correctly registered to the ChR2+ neurons. A rat with the ONI implanted can have blue light transmitted to the ChR2+ neurons. The fiber guide can be attached with cranioplastic cement and an optical fiber inserted into the guide.

Steps 225 and 220 may be performed in either order, or in an integrated concurrent or simultaneous fashion, and are hence shown on the same vertical level of FIG. 2, in accordance with previously-disclosed methods (see e.g., Zhang, F., L. P. Wang, E. S. Boyden, and K. Deisseroth, “Channelrhodopsin-2 and optical control of excitable cells”, Nat Methods, 2006. 3(10): p. 785-92; and Aravanis, A. M. et al. An Optical Neural Interface In Vivo Control of Rodent Motor Cortex with Integrated Fiberoptic and Optogenetic Technology. Journal of Neural Engineering, 2007, as well as the above-mentioned patent documents. In step 230 the stimulation device is turned on, as also described in the above-mentioned documents.

Various implementations of the present invention would activate or affect difference volumes of tissue. Larger volumes of activation could be important in other settings, for example in large-scale neural prosthetic applications. However, measurements and calculations are believed to give rise to a lower limit on volume of tissue activatable with the ONI. Neurons at higher physiological temperatures are believed to be more excitable than those in in vitro experiments in which light power requirements were quantitatively measured. Moreover, while optical fiber can be made relatively thin (e.g., 1.27 mm), enlarging the fiber markedly enlarges the volume of tissue activated (e.g., 20 mm³ for a 1 mm diameter optical fiber).

As an example demonstration of the effectiveness of the present invention as generally applicable to mammalian specimens, the present invention has been applied to control the respective motor functions of various species including, for example, rats and mice. Specifically, by applying the invention to a rat vibrissal motor cortex, whisker movements are evoked as shown in FIG. 3. Also in connection with the present invention, it has been discovered that pulsed blue light delivered via the optical neural interface repeatedly evokes whisker deflections in the rat of up to 10°. The mean number of whisker deflection events during stimulation is significantly higher in the ChR2+ rats than in the ChR2− control rats (p<0.05).

In accordance with the present invention, FIGS. 3a, 3b and 3c illustrate a specific optical neural interface as demonstrated to optically control the motor output of a rat. FIG. 3a is a schematic of a whisker movement measurement arrangement using optical neural interface to activate rat vibrissal motor cortex: the blue laser diode was coupled to a 200 μm multi-mode silica-core optical fiber. The fiber was directed at the motor cortex using the implanted fiber guide. Blue light (473 nm) was transmitted to the vibrissal motor cortex via the optical fiber. Whisker movements were measured magnetically; a magnetic particle was attached to the contralateral C2 vibrissa and a magnetoresistive sensor was placed near the particle. Changes in the voltage were amplified electronically and recorded to a computer. The signal was high-pass filtered at 10 Hz to remove low-frequency drift. FIG. 3b shows whisker activity in a ChR2+ rat in response to a 20 s continuous pulse of blue light. The scale bars are 5° and 5 s. FIG. 3c shows rat mean whisker activity pre-stimulus, intra-stimulus, and post-stimulus. The mean number of whisker twitching events was significantly greater in the ChR2+ rats (lentivirus injected through the fiber guide, n=2) than in the ChR2− rats (vehicle injected through fiber guide, n=2), *p<0.05.

Relative to electrode-based cell stimulation as illustrated in FIG. 4a , FIG. 4b illustrates optical stimulation of genetically-targeted cells. FIG. 4b shows ChR2 expression to a specific neuron population. In this example, ChR2 expression is specific to the excitatory CaMKIIα-expressing cortical neuron population. Thus, one embodiment of the optical neural interface is particularly useful for activating the specific target cells without affecting other cells (e.g., activating excitatory cortical neurons and not other cell types such as inhibitory neurons or glial cells). Embodiments of the present invention also allow for the use of both electrical and optical stimulation.

FIG. 5 shows an example of an optical neural interface (ONI) device for optically stimulating target cells 502. Cannula 506 is inserted through the skull 504 of the patient. This can be done using a variety of surgical procedures, such as a sterotatic surgery. Once cannula 506 is properly positioned, genetic modifiers are introduced to target cells 502 through cannula 506. Subsequently, a light deliver mechanism 508 uses cannula 506 to deliver light to the target cells. In a specific example, light delivery mechanism 508 includes an optical fiber that is inserted through cannula 506. Another implementation uses a combination of mirrors and/or lens elements to direct light to the target cells.

Control 510 may modify the properties of the optical pulses (e.g., frequency, intensity and duration). In a particular embodiment, control 510 includes one or more lasers that generate light at a frequency that corresponds to the optical properties of the target cells. For instance, cells modified with ChR2 have been shown to respond to light corresponding to wavelengths around 400 to 900 nm, and more particularly, to wavelengths of about 470 nm. In addition to providing or controlling the wavelength of the light, the power and temporal characteristics of the light may also be controlled. By varying the intensity or power of the light, the strength of the reaction from the target cells 502 may be varied accordingly. Due to diffusion of the light within the tissue, the intensity of the light generally reduces as the distance from the light source increases. Thus, by increasing the intensity of the light the amount of tissue receiving enough light to activate the light responsive channels or pumps can be increased.

According to a specific embodiment of the present invention, the optical stimulus may be directed at specific target area(s) within the target tissue. In one instance, micro-Electro-Mechanical Systems (MEMS) or servo controlled oscillating mirrors can be used to direct the optical stimulus at a specific location or stimulus point. The stimulus point can be further focused using an objective lens. In a particular embodiment, a scanning microscopy technique, such as laser scanning confocal microscopy, is used to direct the light toward the desired stimulus point. In this manner, light may be scanned across the target cells. The effectiveness and/or results of stimulus at each location within the scan can be monitored and used to determine the most desirable treatment. In another instance, a specific target cell area may be targeted or certain portions of the target cells may be stimulated in a specific sequence.

According to another embodiment of the present invention, the cannula may be inserted near various nerves or muscles. In a particular example of such a use, the cannula may be inserted near various portions of the conduction system of the heart. As an example, the cannula may be inserted near the sinoatrial node (SA) of a patient who exhibits cardiac pacing abnormalities, such as tachycardia and bradycardia. The stimulus may then be used to increase the heart rate (for bradycardia), decrease the heart rate (for tachycardia) or otherwise control the heart rate. Pacing the heart using externally generated electrical pulses (e.g., from electrical contacts) may produce unwanted capture characteristics, such as long QRS waves, and may also suffer from increasing voltage thresholds due to anodal blocking. Optical stimulus may be particularly useful for generating a pseudo-intrinsic pulse (e.g., a pulse voltage that originates from an action potential rather than an electrical contact).

In various embodiments, the cannula may be implemented with at least a portion of the cannula that is flexible. For instance, the cannula may function as a catheter that can be inserted through veins or arteries and into the heart. A fixation device may be included to attach one end of the cannula near the target cells. For further details on catheter devices and their use in cardiac applications, reference may be made to U.S. Pat. No. 4,559,951 to Dahl et al. and entitled “Catheter Assembly,” which is fully incorporated herein by reference.

FIG. 6 shows an example of an optical neural interface used for endocardial stimulation of the heart; according to an example embodiment of the present invention. The genetic modifiers are guided to the desired location using the cannula 602. The cannula 602 is guided into the heart through various techniques, such as those used in connection with the implantation of electrical pacing systems. For instance, the cannula can be fed through one of several veins or arteries into the desired atrium or ventricle of the heart. In a specific example, the cannula is fed into the right atrium to a location near the SA 604. The cannula maybe affixed to (or near) the SA using tines, a screw, barbs or other suitable attachment mechanisms. The genetic modifiers can then be delivered to the target neural cells within the SA. Fiber optics is then inserted through cannula 602 and optical stimulus may then be used to pace or otherwise control the heart.

FIG. 7 shows an example of an optical neural interface used for epicardial stimulation of the heart; according to an example embodiment of the present invention. The cannula 702 is surgically implanted near or into the epicardial (exterior wall) of the heart to allow for stimulus of the target cells 706. The genetic modifiers and optical stimulus are delivered via the inner lumen 704 of the cannula 702. In some instances, the use of optical stimulus in place of other stimulus methods, such as electrical stimulus via electrodes, may result in distinct stimulus characteristics. For instance, electrical conductivity of tissue often does not correspond to optical diffusion characteristics, electrical stimulus may be difficult to direct, and optical diffusion does not necessarily correspond to electrical fields and current flow.

While the invention is not so limited, various aspects of the invention may be better understood in the context of specific embodiments of the invention. According to one such embodiment, a solid-state laser diode that can be pulsed with millisecond precision and that outputs 20 mW of power at 473 nm is coupled to a lightweight, flexible multimode optical fiber that is about 200 μm in diameter. Specific targeting of ChR2 in excitatory cells in vivo may be accomplished using the CaMKIIα promoter. Under these conditions, the power density of light exiting the fiber (e.g., around 380 mW/mm) has been found to be sufficient for driving excitatory neurons in vivo and control motor cortex function in intact rodents. For animals with naturally occurring all-trans-retinal (ATR) in sufficient quantities, such as mammals, no exogenous chemical cofactor is needed.

The in vivo tissue may produce significant attenuation of the laser intensity. Notwithstanding, a power density of light exiting the fiber end at 380 mW/mm² is believed to be sufficient to excite ChR2+ neurons within millimeters of the fiber end.

A specific embodiment of the present invention may be explained in connection with the following methodology as conducted on mammalian subjects. Rats (male Wistars, 250-350 g) and mice (female C57/BL6, 25-30 g) were anaesthetized by i.p. injection (90 mg ketamine and 5 mg xylazine per kg of rat body weight). A concentrated lentivirus solution was stereotactically injected into the rat motor cortex (anteroposterior=−1.5 mm from bregma; lateral=1.5 mm; ventral=1.5 mm) using an ONI device. For electrophysiological experiments, 2 weeks post-injection, 250 μm cortical slices were prepared in ice-cold cutting buffer (64 mM NaCl, 25 mM NaHCO³, 10 mM glucose, 120 mM sucrose, 2.5 mM KCl, 1.25 mM NaH₂PO₄, 0.5 mM CaCl₂ and 7 mM MgCl₂, equilibrated with 95% O₂/5% CO₂) using a vibratome (VT 1000 S; Leica). After a recovery period of 30 min in cutting buffer at 32-35° C., slices were gently removed to a recording chamber mounted on an upright microscope (DM LFSA, Leica) and continuously perfused at a rate of 3-5 ml/min with carbonated ACSF (124 mM NaCl, 3 mM KCl, 26 mM NaHCO³, 1.25 mM NaH₂PO₄, 2.4 mM CaCl₂, 1.3 mM MgCl₂, 10 mM Glucose), ventilated with 95% O₂/5% CO₂.

Motor cortex slices were visualized by standard transmission optics on an upright fluorescence microscope (DM LFSA; Leica) with a 20×, 0.5 NA water immersion objective. mCherry expressing cells located about 10-30 μm below the surface of the slice were visualized with a TXRED filter set (TXRED 4040B, exciter 562 nm, dichroic 530-585 nm, emitter 624 nm; Semrock). Images were recorded with a cooled CCD camera (Retiga Exi; Qimaging). Electrophysiological recordings in neurons were performed. For instance, membrane currents were measured with the patch-clamp technique in the whole cell voltage-clamp configuration using Axon Multiclamp 700B (Axon Instruments) amplifiers. Pipette solution consisted of (in mM): 97 potassium gluconate, 38 KCl, 6 NaCl, 0.35 sodium ATP, 4 magnesium ATP, 0.35 EGTA, 7 phosphocreatine and 20 HEPES (pH 7.25 with KOH). Pipette resistance was 4-8 MΩ. To obtain an estimate of the resting potential, the membrane potential at the time of establishing the whole cell configuration was recorded. pClamp 9 software (Axon Instruments) was used to record all data. For ChR2 activation, blue light pulses were generated using the DG-4 high-speed optical switch with a 300 W xenon lamp (Sutter Instruments) and a GFP filter set (excitation filter HQ470/40X, dichroic Q495LP; Chroma). The light pulses were delivered to the slice through a 20× objective lens (NA 0.5; Leica) yielding a blue light power density of 10 mW/mm², measured with a power meter (1815-C; Newport). Electrophysiological experiments were performed at room temperature (22-24° C.).

Light transmission measurements were conducted with acute brain slices from a 300 g rat and a 30 g mouse. Brain slices of thicknesses between 200 μm and 1 mm were cut in 0-4° C. sucrose solution using a vibratome (Leica; VT1000S). The brain slices were then placed in a Petri dish containing the same sucrose solution over the photodetector of a power meter (ThorLabs; S130A). The tip of a 200 μm optical fiber (BFL37-200; Thorlabs) coupled to a blue diode laser (473 nm, Crystal Laser) was mounted on a micromanipulator and then positioned over the cortical tissue in the slice, normal to the slice and detector. The tip was submerged into the solution and moved to 1 mm above the tissue surface. Blue light from the diode laser was delivered to the tissue via the optical fiber and a measurement of the total light power was recorded from the power meter. The fiber tip was then translated horizontally, so that a blank measurement without tissue present could be taken. For each slice, 1 measurement was taken from each hemisphere. For each tissue thickness value, 2 different slices were cut and measured. Transmission fraction was calculated as the power with tissue present divided by the power with no tissue present. Transmission of light through the brain slices was modeled using the Kubelka-Munk model for diffuse scattering media, T=1/(Sx+1), where T is transmission fraction, S is the scatter coefficient per unit thickness, and x is the thickness of the sample. The model assumes that the sample is a planar, homogeneous, ideal diffuser, and illuminated on one side with diffuse monochromatic light. The model further assumes that reflection and absorption are constant over the thickness of the sample. To further simplify the model, it was also assumed that no absorption occurs. This assumption is based on previous in vivo and in vitro data showing that in mammalian brain tissue, transmission loss from scattering is much greater than loss from absorption for wavelengths ranging from 400 to 900 nm. Best fit values for S were 11.2 mm⁻¹ for mouse and 10.3 mm⁻¹ for rat. The relationship of power density to tissue penetration distance was estimated by taking the product of the measured transmission fraction (remaining light not scattered or absorbed) and the calculated fractional decrease in power density due to the conical geometry of emitted light at a given distance in the absence of tissue scattering and absorption. The geometric decrease in power density with distance from the fiber end x was calculated using the NA (0.37) of the optical fiber, I(x)/I(o)=y²/((Sx+1)(x+y)²), (geometric component only) where

${y = {r\sqrt{\left( \frac{n}{NA} \right)^{2} - 1}}},$ r is the diameter of the optical fiber, and n is the index of refraction of grey matter (e.g., 1.36). The complete expression for power density taking into account both the scattering and geometric losses is

$\frac{I(x)}{I(o)} = {\frac{y^{2}}{\left( {{Sx} + 1} \right)\left( {x + y} \right)^{2}}.}$

Surgeries were performed under aseptic conditions. For anesthesia, ketamine (90 mg/kg of rat body weight; 16 mg/kg of mouse body weight) and xylazine (5 mg/kg of rat body weight; 5 mg/kg of mouse body weight) cocktail was injected i.p. The level of anesthesia was carefully monitored and maintenance doses of anesthesia were given as needed. Fur was sheared from the top of the animal's head and the head was placed in a stereotactic positioning rig. A midline scalp incision was made and a 1-mm-diameter craniotomy was drilled: (rat: anteroposterior=−1.5 mm from bregma, lateral=1.5 mm); (mouse: anteroposterior=−1 mm from bregma, lateral=1 mm). A fiber guide (C313G; Plastics1) was then inserted through the craniotomy to a depth of 1.5 mm in the rat and 1.3 mm in the mouse. Three skull screws (00-96X3/32; Plastics1) were placed in the skull surrounding the fiber guide pedestal, and cranioplastic cement (Ortho-Jet; Lang Dental) was used to anchor the fiber guide system to the skull screws. After 30 minutes, the free edge of the scalp was brought to the base of the cranioplastic cement using sutures (3-0 silk; Ethicon) and tissue adhesive (Vetbond; 3M). A 2 μL aliquot of concentrated lentiviruses in solution (described above) was slowly injected through the fiber guide using an internal cannula (C313I; Plastics1) over 5 minutes. After waiting 10 more minutes for diffusion of the lentivirus, the internal cannula was withdrawn, and a dummy cannula (C313G; Plastics1) was inserted to keep the fiber guide open.

The animals were lightly anesthetized with a 50% dose of the ketamine and xylazine cocktail described above. For these experiments animals were kept in only a lightly sedated state, where whisker deflections spontaneously occurred, as heavier sedation abolished both spontaneous and evoked responses and with no sedation the spontaneous activity was so vigorous it obscured any evoked activity. Whiskers contralateral to the fiber guide implantation were trimmed to 1 cm in length, and a 1 mg rare-earth magnetic particle (neodymium-iron-boron; Magcraft) was attached to the C2 vibrissa. The head was then placed in a stereotactic rig with minimal pressure applied. To measure whisker movement, a magnetoresistive sensor (HMC1001; Honeywell) was mounted on a micromanipulator and moved near the magnetic particle. The signal was amplified (410; Brownlee) and recorded to a computer. Signals were high-pass filtered at 10 Hz to remove low-frequency drift arising from head movement and breathing. Stimulation of ChR2+ neurons was accomplished using a multimode optical fiber (NA 0.37) with a 200 μm silica core (BFL37-200; Thorlabs) coupled to a 473 nm diode pumped laser (20 mW output power uncoupled; Crystal Laser). The measured power density emanating from the fiber was 380 mW/mm². The distal end of the fiber was polished and the jacket was stripped; the fiber was inserted into the fiber guide and advanced until flush with the fiber guide end. The animal was then allowed to habituate to the setup. Experiments were initiated once spontaneous whisker twitches greater than 0.5° were present. During an experimental sweep, 30 s of pre-stimulus data, 20 s of intra-stimulus data (20 s pulse of blue light), and 30 s of post-stimulus data were recorded.

Three weeks after photo stimulation, a subset of mice were anesthetized with ketamine/xylazine and sacrificed by transcardial perfusion with ice cold 4% paraformaldehyde (PFA) in phosphate buffered saline (PBS). Extracted brains were incubated overnight in 4% PFA/PBS and for 48 hours in 30% sucrose/PBS. 40 μm sections were cut on a Leica freezing microtome and stored in cryoprotectant at 4° C. For immunostaining, free-floating sections were rinsed twice in Tris-buffered saline (TBS, pH 7.5) and blocked for 30 minutes in TBS++ (TBS/0.3% Triton X-100/3% Normal Donkey Serum [NDS]). Both primary and secondary antibody incubations were conducted overnight at 4° C. in TBS++ with NDS reduced to 1%; sections were washed repeatedly in TBS after each antibody incubation. Antibodies used were rabbit anti-dsRed (1:500, Clontech), mouse anti-CaMKIIα (1:200; Chemicon), mouse anti-GAD67 (1:500, Chemicon), Cy3 donkey anti-rabbit (1:1000; Jackson ImmunoResearch), and FITC donkey anti-mouse (1:1000, Jackson). Stained sections were mounted under PVA-Dabco (Sigma). Confocal images were acquired on a Leica TCS SP2 microscope.

One of skill in the art would recognize that these methods may be used and modified to be applicable for various animals and human uses. The optical neural interface (ONI) may be particularly useful in functionally activating ChR2 in an intact animal. One instance of the interface consisted of an optical fiber guide stereotactically mounted to the skull with an optical fiber inserted through the guide. The fiber guide is composed of a cannula embedded in a mounting pedestal. For viral transduction of neurons, the fiber guide can serve as an injection cannula to deliver the viral vector to the motor cortex. Then, following expression of ChR2, the cannula is used to guide the optical fiber to the correct location, positioning the tip so the light beam is registered with the ChR2+ neurons. By using the same cannula for viral delivery and positioning of the optical fiber, the light beam is correctly registered to the ChR2+ neurons.

Acute rat brain slices (2 weeks post-injection through the fiber guide with lentivirus carrying the ChR2-mCherry fusion protein) displayed large numbers of red-fluorescent layer 4, 5, and 6 neurons in motor cortex, revealing robust ChR2-mCherry expression. As expected, and required for the optical interface to function, the fluorescent neurons were located on the edge of the potential space created by the fiber guide. At higher magnification, the red fluorescence appeared to be preferentially localized to the plasma membrane in these neurons, consistent with previous observations of mCherry-ChR2 expression. This data suggested that the targeted expression and spatial registration functions of the cannula/fiber guide system could be suitable for implementing an optical neural interface.

To confirm that functional ChR2 could be expressed in the targeted excitatory motor neurons of layer 5 motor cortex, lentivirus carrying the ChR2-mCherry fusion protein under the control of an excitatory neuron-specific CaMKIIα promoter was stereotactically injected into rat vibrissal motor cortex, where brain slices of the injected region made 2 weeks post-injection showed the expected significant red fluorescence (mCherry) in the deeper layers of the cortex. In these same slices, it was next tested whether the level of ChR2 expression in these neurons and with this promoter would be sufficient to induce the depolarizing photocurrents required for action potential generation. Indeed, whole cell recordings obtained from these ChR2+ layer 5 motor neurons in acute brain slices showed robust spiking in response to illumination with blue light (473 nm; 10 mW/mm² generated by a 300 W xenon lamp and 20×, 0.5 NA objective) (FIG. 8a ). In fact, the ChR2+ neurons were able to follow photostimulation trains (10 ms pulses) at 5, 10 and 20 Hz, as shown in FIGS. 8a, 8b and 8c . Moreover, the neurons generated an action potential for every light stimulus; FIG. 8d shows that failures were never observed even over multiple sustained trains of 10 Hz light pulses.

A fiber-coupled diode laser was evaluated for its ability to evoke photocurrent induced action potentials. Whole cell recordings were obtained from a ChR2+ layer 5 motor neuron in acute brain slices prepared as in FIG. 8a-e , illuminated in this case not by the xenon lamp and 20× objective, but by the polished end of a 200 μm multi-mode optical fiber. With the fiber tip placed 1 mm away from the microelectrode tip, the closest distance practically achievable, the neuron perfectly followed a train of photostimuli at 2 Hz (FIG. 8d ). As the frequency increased beyond 2 Hz, there were an increasing number of failures, where the photocurrents evoked were insufficient to depolarize the neuron to the threshold of action potential generation. Since the light intensity exiting the fiber end is quite high (˜380 mW/mm²), the decrease in efficacy with fiber illumination at higher frequencies is likely due to a rapid decrease in the effective light intensity at significant distances distal to the fiber tip. Presumably, ChR2+ neurons close to the fiber received a higher light intensity and therefore followed action potential trains more reliably.

The following discussion addresses various physical processes and device parameters that may be used in determining the volume of ChR2+ neurons that can be effectively photostimulated. Such a volume should correspond to the brain volume in which the light intensity achieved is greater than 1 mW/mm², the minimum intensity required for generation of ChR2-evoked action potentials. The light intensity exiting the 200 μm diameter optical fiber tip is sufficiently intense to evoke action potentials (e.g., around 380 mW/mm²). For these experiments, the blue light used for ChR2 activation (473 nm) is near the ChR2 peak absorption wavelength, but brain tissue highly scatters and weakly absorbs light at this wavelength. A direct measurement of the transmission fraction of total transmitted blue light as a function of distance through the rat and mouse cortical tissue was made. FIG. 9A shows that after passing through 100 μm of cortical tissue, total transmitted light power was reduced by 50%, and by 90% at 1 mm. Similar results were obtained in rat and mouse tissue, and both sets of data corresponded very well with the Kubelka-Munk model for diffuse scattering media, with best fit values for S of 11.2 mm⁻¹ for mouse and 10.3 mm⁻¹ for rat.

In addition to loss of light from scattering and absorption, light intensity also decreases as a result of the conical spreading of light after it exits the optical fiber. The light exiting the multimode fiber is not collimated and spreads with a conical angle of 32° determined by the numerical aperture of 0.37. This effect will reduce the power density of light, which may be a relevant quantitative parameter for determining efficacy of ChR2 stimulation. FIGS. 9A and 9B show the effective light density or intensity as calculated, taking into account the combined effects of scattering, absorption, and conical spread. The relationship of power density to tissue penetration distance was estimated by taking the product of the measured transmission fraction (total remaining light not scattered or absorbed) and the calculated fractional decrease in power density due to the conical geometry of emitted light at a given distance in the absence of tissue scattering and absorption. Using these experimental observations and calculations (e.g., FIG. 9B), the expected volume of tissue activated by this implementation of the optical neural interface was estimated. If effective ChR2-induced spiking is achieved at 1 mW/mm², then with the current laser diode and fiber optic technology the optical neural interface in principle will be capable of evoking spiking in neurons at least up to 1.4 mm from the fiber tip. This distance value, together with the measured conical cross-section of 1 mm diameter at 1.4 mm from the fiber tip, results in a total volume experiencing ≥1 mW/mm² light intensity of ˜0.5 mm³. This volume represents a substantial volume of brain tissue on the same order of magnitude as features on the somatotopic maps on motor cortex, and indicated to us that the optical design of the neural interface, in combination with the previously tested genetic design, could suffice to drive motor cortex function in the intact animal.

It was also tested whether the optical neural interface could be used to control motor output. Having demonstrated that functional ChR2 can be expressed in the deeper layers of vibrissal motor cortex, it was believed that activation of these neurons using the optical neural interface would cause detectable whisker movements. Previous work has shown that electrical stimulation of vibrissal motor cortex results in whisker deflections, and that firing of even a single layer 5 or 6 motor neuron will evoke deflections.

The laboratory rat is a widely used animal model for many neurological and psychiatric diseases relevant to brain stimulation work. However, mice are the ideal animal model for studying genetic contributions to nervous system physiology and pathology, despite the fact that mice can be more challenging for neural interface work due to their much smaller size. Therefore, the optical neural interfaces were also implanted and tested in mice. FIG. 10A shows that, as in the rat, 20-second blue light pulses delivered with the ONI evoked whisker deflections up to 20°. FIG. 10B shows that the mean number of deflections during the stimulus period was significantly higher in the ChR2+ mice than in the ChR2− mice (p<0.05). FIGS. 10C and 10D show that the amplitude of the whisker deflections demonstrated an increase during the stimulus period when compared with pre-stimulus period (p<0.05). Together, these data demonstrate successful implementation of an optical neural interface.

Confirmation of whether a select genetically defined set of neurons were in fact being stimulated via this integrated optical and genetic technology was obtained by employing immunohistochemistry to verify that ChR2 was expressed specifically in the excitatory cortical pyramidal neurons, as hypothesized from the use of the glutamatergic, neuron-specific, CaMKIIα promoter to drive ChR2 expression. Fixed brain sections of injected animals were immunostained as floating sections with an antibody for dsRed to label ChR2-mCherry, along with antibodies for either CaMKIIα or glutamate decarboxylase (GAD67), a GABA-producing enzyme that is specifically expressed in inhibitory interneurons. Representative confocal images of ChR2/CaMKIIα and ChR2/GAD67 immunostaining were taken for confirmation purposes. Nearly all of the ChR2-positive cells in the cortex also expressed CaMKIIα, and almost none expressed GAD67. Thus, ChR2 expression was specific to the excitatory CaMKIIα-expressing cortical neuron population. One embodiment of the optical neural interface may be particularly useful for activating the specific target cells without affecting other cells (e.g., activating excitatory cortical neurons and not other cell types such as inhibitory neurons or glial cells).

Many human applications of the present invention require FDA-approval prior to their use. For instance, human use of gene therapy may require such approval. However, similar gene therapies in neurons (nonproliferative cells that are non-susceptible to neoplasms) are proceeding rapidly, with active, FDA-approved clinical trials already underway involving viral gene delivery to human brains. This is likely to facilitate the use of various embodiments of the present invention for a large variety of applications. The following is a non-exhaustive list of a few examples of such applications and embodiments.

Addiction is associated with a variety of brain functions, including reward and expectation. Additionally, the driving cause of addiction may vary between individuals. According to one embodiment, addiction, for example nicotine addiction, may be treated with optogenetic stabilization of small areas on the insula. Optionally, functional brain imaging—for example cued-state PET or fMRI—may be used to locate a hypermetabolic focus in order to determine a precise target spot for the intervention on the insula surface.

Optogenetic excitation of the nucleus accumbens and septum may provide reward and pleasure to a patient without need for resorting to use of substances, and hence may hold a key to addiction treatment. Conversely, optogenetic stabilization of the nucleus accumbens and septum may be used to decrease drug craving in the context of addiction. In an alternative embodiment, optogenetic stabilization of hypermetabolic activity observed at the genu of the anterior cingulate (BA32) can be used to decrease drug craving. Optogenetic stabilization of cells within the arcuate nucleus of the medial hypothalamus which contain peptide products of pro-opiomelanocortin (POMC) and cocaine-and-amphetamine-regulating transcript (CART) can also be used to decrease drug addiction behavior. For further information in this regard, reference may be made to: Naqvi N H, Rudrauf D, Damasio H, Bechara A. Damage to the insula disrupts addiction to cigarette smoking. Science. 2007 Jan. 26; 315(5811):531-534, which is fully incorporated herein by reference.

Optogenetic stimulation of neuroendocrine neurons of the hypothalamic periventricular nucleus that secrete somatostatin can be used to inhibit secretion of growth hormone from the anterior pituitary, for example in acromegaly. Optogenetic stabilization of neuroendocrine neurons that secrete somatostatin or growth hormone can be used to increase growth and physical development. Among the changes that accompany “normal” aging, is a sharp decline in serum growth hormone levels after the 4^(th) and 5^(th) decades. Consequently, physical deterioration associated with aging may be lessened through optogenetic stabilization of the periventricular nucleus.

Optogenetic stabilization of the ventromedial nucleus of the hypothalamus, particularly the pro-opiomelanocortin (POMC) and cocaine-and-amphetamine-regulating transcript (CART) of the arcuate nucleus, can be used to increase appetite, and thereby treat anorexia nervosa. Alternatively, optogenetic stimulation of the lateral nuclei of the hypothalamus can be used to increase appetite and eating behaviors.

Optogenetic excitation in the cholinergic cells of affected areas including the temporal lobe, the NBM (Nucleus basalis of Meynert) and the posterior cingulate gyrus (BA 31) provides stimulation, and hence neurotrophic drive to deteriorating areas. Because the affected areas are widespread within the brain, an analogous treatment with implanted electrodes may be less feasible than an opto-genetic approach.

Anxiety disorders are typically associated with increased activity in the left temporal and frontal cortex and amygdala, which trends toward normal as anxiety resolves. Accordingly, the affected left temporal and frontal regions and amygdala may be treated with optogenetic stabilization, so as to dampen activity in these regions.

In normal physiology, photosensitive neural cells of the retina, which depolarize in response to the light that they receive, create a visual map of the received light pattern. Optogenetic ion channels can be used to mimic this process in many parts of the body, and the eyes are no exception. In the case of visual impairment or blindness due to damaged retina, a functionally new retina can be grown, which uses natural ambient light rather than flashing light patterns from an implanted device. The artificial retina grown may be placed in the location of the original retina (where it can take advantage of the optic nerve serving as a conduit back to the visual cortex). Alternatively, the artificial retina may be placed in another location, such as the forehead, provided that a conduit for the depolarization signals are transmitted to cortical tissue capable of deciphering the encoded information from the optogenetic sensor matrix. Cortical blindness could also be treated by simulating visual pathways downstream of the visual cortex. The stimulation would be based on visual data produced up stream of the visual cortex or by an artificial light sensor.

Treatment of tachycardia may be accomplished with optogenetic stimulation to parasympathetic nervous system fibers including CN X or Vagus Nerve. This causes a decrease in the SA node rate, thereby decreasing the heart rate and force of contraction. Similarly, optogenetic stabilization of sympathetic nervous system fibers within spinal nerves T1 through T4, serves to slow the heart. For the treatment of pathological bradycardia, optogenetic stabilization of the Vagus nerve, or optogenetic stimulation of sympathetic fibers in T1 through T4 will serve to increase heart rate. Cardiac disrhythmias resulting from aberrant electrical foci that outpace the sinoatrial node may be suppressed by treating the aberrant electrical focus with moderate optogenetic stabilization. This decreases the intrinsic rate of firing within the treated tissue, and permits the sinoatrial node to regain its role in pacing the heart's electrical system. In a similar way, any type of cardiac arrhythmia could be treated. Degeneration of cardiac tissue that occurs in cardiomyopathy or congestive heart failure could also be treated using this invention; the remaining tissue could be excited using various embodiments of the invention.

Optogenetic excitation stimulation of brain regions including the frontal lobe, parietal lobes and hippocampi, may increase processing speed, improve memory, and stimulate growth and interconnection of neurons, including spurring development of neural progenitor cells. As an example, one such application of the present invention is directed to optogenetic excitation stimulation of targeted neurons in the thalamus for the purpose of bringing a patient out of a near-vegetative (barely-conscious) state. Consistent with the flow chart of FIG. 2 and other embodiments discussed herein, an elongated delivery structure is inserted into a narrow passageway of the patient's skull for inducing growth of light-gated ion channels or pumps in the membrane of targeted thalamus neurons. These modified neurons are then stimulated, e.g., via optics which may also gain access by the same passageway, by directing a flash of light thereupon so as to modulate the function of the targeted neurons and/or surrounding cells. For further information regarding appropriate modulation techniques (via electrode-based treatment) or further information regarding the associated brain regions for such patients, reference may be made to: Schiff N D, Giacino J T, Kalmar K, Victor J D, Baker K, Gerber M, Fritz B, Eisenberg B, O'Connor J O, Kobylarz E J, Farris S, Machado A, McCagg C, Plum F, Fins J J, Rezai A R. Behavioral improvements with thalamic stimulation after severe traumatic brain injury. Nature. Vol 448. Aug. 2, 2007 pp 600-604.

In an alternative embodiment, optogenetic excitation may be used to treat weakened cardiac muscle in conditions such as congestive heart failure. Electrical assistance to failing heart muscle of CHF is generally not practical, due to the thin-stretched, fragile state of the cardiac wall, and the difficulty in providing an evenly distributed electrical coupling between an electrodes and muscle. For this reason, preferred methods to date for increasing cardiac contractility have involved either pharmacological methods such as Beta agonists, and mechanical approaches such as ventricular assist devices. In this embodiment of the present invention, optogenetic excitation is delivered to weakened heart muscle via light emitting elements on the inner surface of a jacket surround the heart or otherwise against the affected heart wall. Light may be diffused by means well known in the art, to smoothly cover large areas of muscle, prompting contraction with each light pulse.

Optogenetic stabilization in the subgenual portion of the cingulate gyms (Cg25), yellow light may be applied with an implanted device. The goal would be to treat depression by suppressing target activity in manner analogous to what is taught by Mayberg H S et al., Deep Brain Stimulation for Treatment-Resistant Depression. Neuron, Vol. 45, 651-660, Mar. 3, 2005, 651-660, which is fully incorporated herein by reference. In an alternative embodiment, an optogenetic excitation stimulation method is to increase activity in that region in a manner analogous to what is taught by Schlaepfer et al., Deep Brain stimulation to Reward Circuitry Alleviates Anhedonia in Refractory Major Depression, Neuropsychopharmacology 2007 1-10, which is fully incorporated herein by reference. In yet another embodiment the left dorsolateral prefrontal cortex (LDPFC) is targeted with an optogenetic excitation stimulation method. Pacing the LDLPFC at 5-20 Hz serves to increase the basal metabolic level of this structure which, via connecting circuitry, serves to decrease activity in Cg 25, improving depression in the process. Suppression of the right dorsolateral prefrontal cortex (RDLPFC) is also an effective depression treatment strategy. This may be accomplished by optogenetic stabilization on the RDLPFC, or suppression may also be accomplished by using optogenetic excitation stimulation, and pulsing at a slow rate—1 Hz or less, improving depression in the process. Vagus nerve stimulation (VNS) may be improved using an optogenetic approach. Use of optogenetic excitation may be used in order to stimulate only the vagus afferents to the brain, such as the nodose ganglion and the jugular ganglion. Efferents from the brain would not receive stimulation by this approach, thus eliminating some of the side-effects of VNS including discomfort in the throat, a cough, difficulty swallowing and a hoarse voice. In an alternative embodiment, the hippocampus may be optogenetically excited, leading to increased dendritic and axonal sprouting, and overall growth of the hippocampus. Other brain regions implicated in depression that could be treated using this invention include the amygdala, accumbens, orbitofrontal and orbitomedial cortex, hippocampus, olfactory cortex, and dopaminergic, serotonergic, and noradrenergic projections. Optogenetic approaches could be used to control spread of activity through structures like the hippocampus to control depressive symptoms.

So long as there are viable alpha and beta cell populations in the pancreatic islets of Langerhans, the islets can be targeted for the treatment of diabetes. For example, when serum glucose is high (as determined manually or by closed loop glucose detection system), optogenetic excitation may be used to cause insulin release from the beta cells of the islets of Langerhans in the pancreas, while optogenetic stabilization is used to prevent glucagon release from the alpha cells of the islets of Langerhans in the pancreas. Conversely, when blood sugars are too low (as determined manually or by closed loop glucose detection system), optogenetic stabilization may be used to stop beta cell secretion of insulin, and optogenetic excitation may be used to increase alpha-cell secretion of glucagon.

For treatment of epilepsy, quenching or blocking epileptogenic activity is amenable to optogenetic approaches. Most epilepsy patients have a stereotyped pattern of activity spread resulting from an epileptogenic focus Optogenetic stabilization could be used to suppress the abnormal activity before it spreads or truncated it early in its course. Alternatively, activation of excitatory tissue via optogenetic excitation stimulation could be delivered in a series of deliberately ansynchronous patterns to disrupt the emerging seizure activity. Another alternative involves the activation of optogenetic excitation stimulation in GABAergic neurons to provide a similar result. Thalamic relays may be targeted with optogenetic stabilization triggered when an abnormal EEG pattern is detected.

Another embodiment involves the treatment of gastrointestinal disorders. The digestive system has its own, semi-autonomous nervous system containing sensory neurons, motor neurons and interneurons. These neurons control movement of the GI tract, as well as trigger specific cells in the gut to release acid, digestive enzymes, and hormones including gastrin, cholecystokinin and secretin. Syndromes that include inadequate secretion of any of these cellular products may be treated with optogenetic stimulation of the producing cell types, or neurons that prompt their activity. Conversely, optogenetic stabilization may be used to treat syndromes in which excessive endocrine and exocrine products are being created. Disorders of lowered intestinal motility, ranging from constipation (particularly in patients with spinal cord injury) to megacolan may be treated with optogenetic excitation of motor neurons in the intestines. Disorders of intestinal hypermotility, including some forms of irritable bowel syndrome may be treated with optogenetic stabilization of neurons that control motility. Neurogentic gastric outlet obstructions may be treated with optogenetic stabilization of neurons and musculature in the pyloris. An alternative approach to hypomobility syndromes would be to provide optogenetic excitation to stretch-sensitive neurons in the walls of the gut, increasing the signal that the gut is full and in need of emptying.

In this same paradigm, an approach to hypermobility syndromes of the gut would be to provide optogenetic stabilization to stretch receptor neurons in the lower GI, thus providing a “false cue” that the gut was empty, and not in need of emptying. In the case of frank fecal incontinence, gaining improved control of the internal and external sphincters may be preferred to slowing the motility of the entire tract. During periods of time during which a patient needs to hold feces in, optogenetic excitation of the internal anal sphincter will provide for retention. Providing optogenetic stimulation to the external sphincter may be used to provide additional continence. When the patient is required to defecate, the internal anal sphincter, and then external anal sphincter should be relaxed, either by pausing the optogenetic stimulation, or by adding optogenetic stabilization.

Conductive hearing loss may be treated by the use of optical cochlear implants. Once the cochlea has been prepared for optogenetic stimulation, a cochlear implant that flashes light may be used. Sensorineural hearing loss may be treated through optical stimulation of downstream targets in the auditory pathway.

Another embodiment of the present invention is directed toward the treatment of blood pressure disorders, such as hypertension. Baroreceptors and chemoreceptors in regions such as the aorta (aortic bodies and paraaortic bodies) and the carotid arteries (“carotic bodies”) participate the regulation of blood pressure and respiration by sending afferents via the vagus nerve (CN X), and other pathways to the medulla and pons, particularly the solitary tract and nucleus. Optogentetic excitation of the carotid bodies, aortic bodies, paraortic bodies, may be used to send a false message of “hypertension” to the solitary nucleus and tract, causing it to report that blood pressure should be decreased. Optogenetic excitation or stabilization directly to appropriate parts of the brainstem may also be used to lower blood pressure. The opposite modality causes the optogenetic approach to serve as a pressor, raising blood pressure. A similar effect may also be achieved via optogenetic excitation of the Vagus nerve, or by optogenetic stabilization of sympathetic fibers within spinal nerves T1-T4. In an alternative embodiment, hypertension may be treated with optogenetic stabilization of the heart, resulting in decreased cardiac output and lowered blood pressure. According to another embodiment, optogentic stabilization of aldosterone-producing cells within the adrenal cortex may be used to decrease blood pressure. In yet another alternative embodiment, hypertension may be treated by optogenetic stabilization of vascular smooth muscle. Activating light may be passed transcutaneously to the peripheral vascular bed.

Another example embodiment is directed toward the treatment of hypothalamic-pituitary-adrenal axis disorders. In the treatment of hypothyroidism, optogenetic excitation of parvocellular neuroendocrine, neurons in the paraventricular and anterior hypothalamic nuclei can be used to increase secretion of thyrotropin-releasing hormone (TRH). TRH, in turn, stimulates anterior pituitary to secrete TSH. Conversely, hyperthyroidism may be treated with optogenetic stabilization of the provocellular neuroendocrine neurons. For the treatment of adrenal insufficiency, or of Addison's disease, optogenetic excitation of parvocellular neuroendocrine neurons in the supraoptic nucleus and paraventricular nuclei may be used to increase the secretion of vasopressin, which, with the help of corticotropin-releasing hormone (CRH), stimulate anterior pituitary to secrete ACTH. Cushing syndrome, frequently caused by excessive ACTH secretion, may be treated with optogenetic stabilization of the parvocellular neuroendocrine neurons of supraoptic nucleus via the same physiological chain of effects described above. Neuroendocrine neurons of the arcuate nucleus produce dopamine, which inhibits secretion of prolactin from the anterior pituitary. Hyperprolactinemia can therefore be treated via optogenetic excitation, while hypoprolactinemia can be treated with optogenetic stabilization of the neuroendocrine cells of the arcuate nucleus.

In the treatment of hyperautonomic states, for example anxiety disorders, optogenetic stabilization of the adrenal medulla may be used to reduce norepinephrine output. Similarly, optogenetic stimulation of the adrenal medulla may be used in persons with need for adrenaline surges, for example those with severe asthma, or disorders that manifest as chronic sleepiness.

Optogenetic stimulation of the adrenal cortex will cause release of chemicals including cortisol, testosterone, and aldosterone. Unlike the adrenal medualla, the adrenal cortex receives its instructions from neuroendocrine hormones secreted from the pituitary and hypothalamus, the lungs, and the kidneys. Regardless, the adrenal cortex is amenable to optogenetic stimulation. Optogenetic stimulation of the cortisol-producing cells of the adrenal cortex may be used to treat Addison's disease. Optogenetic stabilization of cortisol-producing cells of the adrenal cortex may be used to treat Cushing's disease. Optogenetic stimulation of testosterone-producing cells may be used to treat disorders of sexual interest in women: Optogenetic stabilization of those same cells may be used to decrease facial hair in women. Optogenetic stabilization of aldosterone-producing cells within the adrenal cortex may be used to decrease blood pressure. Optogenetic excitation of aldosterone-producing cells within the adrenal cortex may be used to increase blood pressure.

Optogenetic excitation stimulation of specific affected brain regions may be used to increase processing speed, and stimulate growth and interconnection of neurons, including spurring the maturation of neural progenitor cells as in Deisseroth et al., 2004. Such uses can be particularly useful for treatment of mental retardation.

According to another embodiment of the present invention, various muscle diseases and injuries can be treated. Palsies related to muscle damage, peripheral nerve damage and to dystrophic diseases can be treated with optogenetic excitation to cause contraction, and optogenetic stabilization to cause relaxation. This latter relaxation via optogenetic stabilization approach can also be used to prevent muscle wasting, maintain tone, and permit coordinated movement as opposing muscle groups are contracted. Likewise, frank spasticity can be treated via optogenetic stabilization.

In areas as diverse as peripheral nerve truncation, stroke, traumatic brain injury and spinal cord injury, there is a need to foster the growth of new neurons, and assist with their integration into a functional network with other neurons and with their target tissue. Re-growth of new neuronal tracts may be encouraged via optogenetic excitation, which serves to signal stem cells to sprout axons and dendrites, and to integrate themselves with the network. Use of an optogenetic technique (as opposed to electrodes) prevents receipt of signals by intact tissue, and serves to ensure that new target tissue grows by virtue of a communication set up with the developing neurons, and not with an artificial signal like current emanating from an electrode.

Obesity can be treated with optogenetic excitation to the ventromedial nucleus of the hypothalamus, particularly the pro-opiomelanocortin (POMC) and cocaine-and-amphetamine-regulating transcript (CART) of the arcuate nucleus. In an alternative embodiment, obesity can be treated via optogenetic stabilization of the lateral nuclei of the hypothalamus. In another embodiment, optogenetic stimulation to leptin-producing cells, or to cells with leptin receptors within the hypothalamus may be used to decrease appetite and hence treat obesity.

Destructive lesions to the anterior capsule and analogous DBS to that region are established means of treating severe, intractable obsessive-compulsive disorder 48 (OCD48). Such approaches may be emulated using optogenetic stabilization to the anterior limb of the internal capsule, or to regions such as BA32 and Cg24 which show metabolic decrease as OCD remits.

Chronic Pain can be treated using another embodiment of the present invention. Electrical stimulation methods include local peripheral nerve stimulation, local cranial nerve stimulation and “subthreshold” motor cortex stimulation. Reasonable optogenic approaches include optogenetic stabilization at local painful sites. Attention to promoter selection would ensure that other sensory and motor fibers would be unaffected. Selective optogenetic excitation of interneurons at the primary motor cortex also may provide effective pain relief. Also, optogenetic stabilization at the sensory thalamus, (particularly medial thalamic nuclei), periventricular grey matter, and ventral raphe nuclei, may be used to produce pain relief. In an alternative embodiment, optogenetic stabilization of parvalbumin-expressing cells targeting as targeting strategy, may be used to treat pain by decreasing Substance P production. The release of endogenous opiods may be accomplished by using optogenetic excitation to increase activity in the nucleus accumbens. In an alternative embodiment, when POMC neurons of the arcuate nucleus of the medial hypothalamus are optogenetically excited, beta endorphin are increased, providing viable treatment approaches for depression and for chronic pain.

Parkinson's Disease can be treated by expressing optogenetic stabilization in the glutamatergic neurons in either the subthalamic nucleus (STN) or the globus pallidus interna (GPi) using an excitatory-specific promoter such as CaMKIIα, and apply optogenetic stabilization. Unlike electrical modulation in which all cell-types are affected, only glutamatergic STN neurons would be suppressed.

Certain personality disorders, including the borderline and antisocial types, demonstrate focal deficits in brain disorders including “hypofrontality.” Direct or indirect optogenetic excitation of these regions is anticipated to produce improvement of symptoms. Abnormal bursts of activity in the amygdala are also known to precipitate sudden, unprompted flights into rage: a symptom of borderline personality disorder, as well as other conditions, which can benefit from optogenetic stabilization of the amygdala. Optogenetic approaches could improve communication and synchronization between different parts of the brain, including amygdala, striatum, and frontal cortex, which could help in reducing impulsiveness and improving insight.

The amygdalocentric model of post-traumatic-stress disorder (PTSD) proposes that it is associated with hyperarousal of the amygdala and insufficient top-down control by the medial prefrontal cortex and the hippocampus. Accordingly, PTSD may be treated with optogenetic stabilization of the amygdale or hippocampus.

Schizophrenia is characterized by abnormalities including auditory hallucinations. These might be treated by suppression of the auditory cortex using optogenetic stabilization. Hypofrontality associated with schizophrenia might be treated with optogenetic excitation in the affected frontal regions. Optogenetic approaches could improve communication and synchronization between different parts of the brain which could help in reducing misattribution of self-generated stimuli as foreign.

Optogenetic stabilization of cells within the arcuate nucleus of the medial hypothalamus, which contain peptide products of pro-opiomelanocortin (POMC) and cocaine-and-amphetamine-regulating transcript (CART) can be used to reduce compulsive sexual behavior. Optogentic excitation of cells within the arcuate nucleus of the medial hypothalamus which contain peptide products of pro-opiomelanocortin (POMC) and cocaine-and-amphetamine-regulating transcript (CART) may be used to increase sexual interest in the treatment of cases of disorders of sexual desire. In the treatment of disorders of hypoactive sexual desire testosterone production by the testes and the adrenal glands can be increased through optogenetic excitation of the pituitary gland. Optogentic excitation of the nucleus accumbens can be used for the treatment of anorgasmia.

The suprachiasmatic nucleus secretes melatonin, which serves to regulate sleep/wake cycles. Optogenetic excitation to the suprachiasmic nucleus can be used to increase melatonin production, inducing sleep, and thereby treating insomnia. Orexin (hypocretin) neurons strongly excite numerous brain nuclei in order to promote wakefulness. Optogentetic excitation of orexin-producing cell populations can be used to treat narcolepsy, and chronic daytime sleepiness.

Optogenetic stimulation of the supraoptic nucleus may be used to induce secretion of oxytocin, can be used to promote parturition during childbirth, and can be used to treat disorders of social attachment.

Like muscular palsies, the motor functions that have been de-afferented by a spinal cord injury may be treated with optogenetic excitation to cause contraction, and optogenetic stabilization to cause relaxation. This latter relaxation via optogenetic stabilization approach may also be used to prevent muscle wasting, maintain tone, and permit coordinated movement as opposing muscle groups are contracted. Likewise, frank spasticity may be treated via optogenetic stabilization. Re-growth of new spinal neuronal tracts may be encouraged via optogenetic excitation, which serves to signal stem cells to sprout axons and dendrites, and to integrate themselves with the network.

Stroke deficits include personality change, motor deficits, sensory deficits, cognitive loss, and emotional instability. One strategy for the treatment of stroke deficits is to provide optogenetic stimulation to brain and body structures that have been deafferented from excitatory connections. Similarly, optogenetic stabilization capabilities can be imparted on brain and body structures that have been deafferented from inhibitory connections.

Research indicates that the underlying pathobiology in Tourette's syndrome is a phasic dysfunction of dopamine transmission in cortical and subcortical regions, the thalamus, basal ganglia and frontal cortex. In order to provide therapy, affected areas are preferably first identified using techniques including functional brain imaging and magnetoencephalography (MEG). Whether specifically identified or not, optogenetic stabilization of candidate tracts may be used to suppress motor tics. Post-implantation empirical testing of device parameters reveals which sites of optogenetic stabilization, and which are unnecessary to continue.

In order to treat disorders of urinary or fecal incontinence optogenetic stabilization can be used to the sphincters, for example via optogenetic stabilization of the bladder detrussor smooth muscle or innervations of that muscle. When micturation is necessary, these optogenetic processes are turned off, or alternatively can be reversed, with optogenetic stabilization to the (external) urinary sphincter, and optogenetic excitation of the bladder detrussor muscle or its innervations. When a bladder has been deafferentated, for example, when the sacral dorsal roots are cut or destroyed by diseases of the dorsal roots such as tabes dorsalis in humans, all reflex contractions of the bladder are abolished, and the bladder becomes distended. Optogenetic excitation of the muscle directly can be used to restore tone to the detrussor, prevent kidney damage, and to assist with the micturition process. As the bladder becomes “decentralized” and hypersensitive to movement, and hence prone to incontinence, optogenetic stabilization to the bladder muscle can be used to minimize this reactivity of the organ.

In order to selectively excite/inhibit a given population of neurons, for example those involved in the disease state of an illness, several strategies can be used to target the optogenetic proteins/molecules to specific populations.

For various embodiments of the present invention, genetic targeting may be used to express various optogenetic proteins or molecules. Such targeting involves the targeted expression of the optogenetic proteins/molecules via genetic control elements such as promoters (e.g. Parvalbumin, Somatostatin, Cholecystokinin, GFAP), enhancers/silencers (e.g. Cytomaglovirus Immediate Early Enhancer), and other transcriptional or translational regulatory elements (e.g. Woodchuck Hepatitis Virus Post-transcriptional Regulatory Element). Permutations of the promoter+enhancer+regulatory element combination can be used to restrict the expression of optogenetic probes to genetically-defined populations.

Various embodiments of the present invention may be implemented using spatial/anatomical targeting. Such targeting takes advantage of the fact that projection patterns of neurons, virus or other reagents carrying genetic information (DNA plasmids, fragments, etc), can be focally delivered to an area where a given population of neurons project to. The genetic material will then be transported back to the bodies of the neurons to mediate expression of the optogenetic probes. Alternatively, if it is desired to label cells in a focal region, viruses or genetic material may be focally delivered to the interested region to mediate localized expression.

Various gene delivery systems are useful in implementing one or more embodiments of the present invention. One such delivery system is Adeno-Associated Virus (AAV). AAV can be used to deliver a promoter+optogenetic probe cassett to a specific region of interest. The choice of promoter will drive expression in a specific population of neurons. For example, using the CaMKIIα promoter will drive excitatory neuron specific expression of optogenetic probes. AAV will mediate long-term expression of the optogenetic probe for at least 1 year or more. To achieve more specificity, AAV may be pseudotyped with specific serotypes 1 to 8, with each having different trophism for different cell types. For instance, serotype 2 and 5 is known to have good neuron-specific trophism.

Another gene deliver mechanism is the use of a retrovirus. HIV or other lentivirus-based retroviral vectors may be used to deliver a promoter+optogenetic probe cassette to a specific region of interest. Retroviruses may also be pseudotyped with the Rabies virus envelope glycoprotein to achieve retrograde transport for labeling cells based on their axonal projection patterns. Retroviruses integrate into the host cell's genome, therefore are capable of mediating permanent expression of the optogenetic probes. Non-lentivirus based retroviral vectors can be used to selectively label dividing cells.

Gutless Adenovirus and Herpes Simplex Virus (HSV) are two DNA based viruses that can be used to deliver promoter+optogenetic probe cassette into specific regions of the brain as well. HSV and Adenovirus have much larger packaging capacities and therefore can accommodate much larger promoter elements and can also be used to deliver multiple optogenetic probes or other therapeutic genes along with optogenetic probes.

Focal Electroporation can also be used to transiently transfect neurons. DNA plasmids or fragments can be focally delivered into a specific region of the brain. By applying mild electrical current, surrounding local cells will receive the DNA material and expression of the optogenetic probes.

In another instance, lipofection can be used by mixing genetic material with lipid reagents and then subsequently injected into the brain to mediate transfect of the local cells.

Various embodiments involve the use of various control elements. In addition to genetic control elements, other control elements (particularly promoters and enhancers whose activities are sensitive to chemical, magnetic stimulation, or infrared radiation) can be used to mediate temporally-controlled expression of the optogenetic probes. For example, a promoter whose transcriptional activity is subject to infrared radiation allows one to use focused radiation to fine tune the expression of optogenetic probes in a focal region at only the desired time.

According to one embodiment of the present invention, the ONI device may be used in animal models of DBS, for example in Parkinsonian rats, to identify the target cell types responsible for therapeutic effects (an area of intense debate and immense clinical importance). This knowledge alone may lead to the development of improved pharmacological and surgical strategies for treating human disease.

According to another embodiment of the present invention, genetically-defined cell types may be linked with complex systems-level behaviors, and may allow the elucidation of the precise contribution of different cell types in many different brain regions to high-level organismal functioning.

For further information, citations and background information related to implementation of the above-discussed embodiments, reference may be made to the following documents, each being fully incorporated herein by reference.

-   U.S. Pat. No. 6,810,285 Seizure sensing and detection using an     implantable device. -   U.S. Pat. No. 6,647,296 Implantable apparatus for treating     neurological disorders. -   U.S. Pat. No. 6,597,954 System and method for controlling epileptic     seizures with spatially separated detection and stimulation     electrodes. -   U.S. Pat. No. 6,480,743 System and method for adaptive brain     stimulation. -   U.S. Pat. No. 6,473,639 Neurological event detection procedure using     processed display channel based algorithms and devices incorporating     these procedures. -   U.S. Pat. No. 6,161,045 Method for determining stimulation     parameters for the treatment of epileptic seizures. -   U.S. Pat. No. 6,134,474 Responsive implantable system for the     treatment of neurological disorders. -   Aravanis, A. M. et al. An Optical Neural Interface: In Vivo Control     of Rodent Motor Cortex with Integrated Fiberoptic and Optogenetic     Technology. Journal of Neural Engineering, 2007. -   Benabid A L Future strategies to restore brain functions. Conference     proceedings from Medicine Meets Millennium: World Congress of     Medicine and Health, 2000. -   Boyden, E. S., F. Zhang, E. Bamberg, G. Nagel, and K. Deisseroth,     Millisecond-timescale, genetically targeted optical control of     neural activity. Nat Neurosci, 2005. 8(9): p. 1263-8. -   Deisseroth, K., G. Feng, A. K. Majewska, G. Miesenbock, A. Ting,     and M. J. Schnitzer, Next-generation optical technologies for     illuminating genetically targeted brain circuits. J Neurosci, 2006.     26(41): p. 10380-6. -   Greenberg B D, Malone D A, Friehs G M, Rezai A R, Kubu C S, Malloy P     F, Salloway S P, Okun M S, Goodman W K, Rasmussen S A. Three-year     outcomes in deep brain stimulation for highly resistant     obsessive-compulsive disorder. Neuropsychopharmacology (2006) 31,     2384-2393. -   Mayberg H S, Lozano A M, Voon V, McNeely H E, Seminowicz D, Hamani     C, Schalb J M, Kennedy S H. Deep Brain Stimulation for     Treatment-Resistant Depression. Neuron, Vol. 45, 651-660, Mar. 3,     2005, 651-660. -   Schlaepfer T E, Cohen M X, Frick C, Kosel M, Brodesser D, Axmacher     N, Joe A Y, Kreft M, Lenartz D, Sturm V. Deep Brain stimulation to     Reward Circuitry Alleviates Anhedonia in Refractory Major     Depression. Neuropsychopharmacology 2007 1-10. -   Singer H S, Szymanski S, Giuliano J, Yokoi F, A. Dogan S, Brasic J     R, Zhou Y, Grace A A, and Wong D F. Elevated Intrasynaptic Dopamine     Release in Tourette's Syndrome Measured by PETAm J Psychiatry,     August 2002; 159: 1329-1336; Van der Linden G, van Heerden B,     Warwick J, Wessels C, van Kradenburg J, Zungu-Dirwayi N, Stein D J. -   Functional brain imaging and pharmacotherapy in social phobia:     single photon emission computed tomography before and after     treatment with the selective serotonin reuptake inhibitor     citalopram. Prog Neuropsychopharmacol Biol Psychiatry. 2000 April;     24(3):419-38. -   Zhang, F., L. P. Wang, E. S. Boyden, and K. Deisseroth,     Channelrhodopsin-2 and optical control of excitable cells. Nat     Methods, 2006. 3(10): p. 785-92. -   Zhang F, Wang L P, Brauner M, Liewald J F, Kay K, Watzke N, Wood P     G, Bamberg E, Nagel G, Gottschalk A, Deisseroth K. Multimodal fast     optical interrogation of neural circuitry. Nature. Vol 446 5     Apr. 2007. 633-641. -   Schiff N D, Giacino J T, Kalmar K, Victor J D, Baker K, Gerber M,     Fritz B, Eisenberg B, O'Connor J O, Kobylarz E J, Farris S, Machado     A, McCagg C, Plum F, Fins J J, Rezai A R. Behavioral improvements     with thalamic stimulation after severe traumatic brain injury.     Nature. Vol 448. Aug. 2, 2007 pp 600-604.

The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Based on the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the present invention without strictly following the exemplary embodiments and applications illustrated and described herein. For example, such modifications include combining teachings of the various patent documents cited herein; including as just one example, combining aspects of the teaching from the teachings of above-identified application Ser. No. 11/651,422 entitled System for Optical Stimulation of Target Cells. Such a combination realizes many advantages expressly discussed in each of these patent documents. Such modifications and changes do not depart from the true spirit and scope of the present invention, which is set forth in the following claims. 

What is claimed is:
 1. A system for electrically stimulating target neuronal cells of a living animal in vivo, the system comprising: a) a stereotactic guide; b) an elongated structure configured to be inserted through the stereotactic guide and into a narrow passageway in the animal such that an end of the elongated structure is sufficiently near the target neuronal cells to deliver stimulation thereto; c) a reservoir comprising a composition comprising a recombinant viral vector, wherein the recombinant viral vector comprises a nucleotide sequence encoding a light responsive polypeptide, wherein the light-responsive polypeptide is: i) a channelrhodopsin and comprises an amino acid sequence having at least about 90% amino acid sequence identity to a ChR2 polypeptide; or ii) a halorhodopsin; d) a means for delivering the composition from the reservoir through the elongated structure; e) a flexible optical fiber arrangement configured to be inserted through the stereotactic guide and to stimulate the target neuronal cells by delivering light to the light-responsive polypeptide in the target cells; f) a laser diode coupled to the flexible optical fiber arrangement, wherein the laser diode is capable of at least 20 mW of power output and can be pulsed in a millisecond timeframe; and g) a control device configured to control one or more of the frequency, intensity, and duration of the delivered light.
 2. The system of claim 1, wherein the light-responsive polypeptide comprises an amino acid sequence having at least about 95% amino acid sequence identity to the ChR2 polypeptide, and wherein the nucleotide sequence encoding the light-responsive polypeptide is operably linked to a target cell type-specific promoter.
 3. The system of claim 1, wherein the viral vector is an adeno-associated virus vector or a lentivirus vector.
 4. The system of claim 1, wherein the elongated structure is a cannula.
 5. The system of claim 1, wherein the elongated structure is a catheter.
 6. The system of claim 1, wherein at least a portion of the system is implantable.
 7. The system of claim 1, wherein the viral vector comprises a nucleotide sequence encoding a halorhodopsin.
 8. The system of claim 1, comprising an electrical recording device.
 9. The system of claim 8, wherein the electrical recording device comprises an array of microelectrodes.
 10. The system of claim 1, wherein the flexible optical fiber arrangement has a diameter of about 200 μm. 